1. Field of the Invention
The present disclosure relates to an antenna device to be installed inside a room of a vehicle, and a vehicle antenna in which the antenna device is installed.
2. Description of the Related Art
Usually, an antenna for receiving a radio broadcast or an antenna for receiving a television broadcast is installed in a vehicle. Recently, however, a demand has been growing for installing an antenna for transmitting and receiving vertically polarized radio waves, which have been used for inter-vehicle communication and road-to-vehicle communication in the ITS (Intelligent Transport System: Intelligent Transportation System).
As the antennas for transmitting and receiving the vertically polarized radio waves, there are disclosed a vehicle antenna (Patent Document 1 (Japanese Unexamined Patent Publication No. 2001-44730)) provided with an antenna pattern that is installed to be parallel to a surface of a window glass at a position at an upper part of the interior side of the window glass of the vehicle, to which a rear-view mirror pedestal is to be bonded; and an antenna (Patent Document 2 (Japanese Unexamined Patent Publication No. 2009-188912)) formed of a first radiation conductor and a second radiation conductor, where the first radiation conductor is formed on a vehicle interior side surface of the window glass of the vehicle, and the second radiating conductor is bent toward inside the vehicle so as to form a predetermined angle.
For a case of the vehicle antenna disclosed in Patent Document 1, which is related art, however, there is a problem that, since the antenna pattern is formed that is parallel to the glass surface of the vehicle, transmission and reception sensitivity with respect to vertically polarized waves arriving in a direction horizontal to the ground is affected by an installation angle of the window glass of the vehicle.
For a case of the vehicle antenna disclosed in Patent Document 2, there is also a problem that, since the first radiation conductor is formed on the window glass surface of the vehicle, transmission and reception sensitivity with respect to vertically polarized waves arriving in the direction horizontal to the ground is affected by an installation angle of the window glass of the vehicle.
There is a need for an antenna device that can enhance transmission and reception characteristics with respect to vertically polarized waves arriving in the direction horizontal to the ground, without depending on an installation angle of an window glass of a vehicle.